Optimal conditions for pressure shock induction of triploidy in turbot and a comparison of induction efficiency with cold shock

Abstract

The mass production of triploid turbot Scophthalmus maximus is expected to enhance the economic benefits of aquaculture due to its sterility, growth, and survival advantages. Among the methods for inducing triploidy in teleost, pressure shock has been considered a more consistent and reliable approach. In this study, the optimal parameters for inducing triploidy in turbot through hydrostatic pressure shock were investigated in a series of trials, including the intensity (55–75 MPa), timing (3.5–8.5 min after fertilization, maf) and duration (4–12 min). The ploidy level was determined by flow cytometry analysis. Under a water temperature of 14.5 ± 0.5 °C, treatment optima for pressure shock were determined to be 4.5–5.5 maf with 60 MPa for 6 min, resulting in 100% triploidy rate. A comparison of induction efficiency between pressure shock using this combination and cold shock initiated at 6.5 maf in −2 °C sea water for 25 min was carried out using eggs from three females. The higher hatching rates and triploidy rates, and lower abnormality rates were investigated with pressure shock treatment compared with cold shock treatment. The optimized parameters were successfully applied to three large batches of eggs (∼ 250, 300 and 330 mL) for mass production of triploid turbot. The total length and body weight of triploids were significantly lower than those of diploid counterparts at 2 months after hatching (mah), however, they exhibited a significant increase at 8 and 11 mah, respectively, and maintained this higher level thereafter. Additionally, the survival rates remained similar from 2 to 12 mah. The results of this preliminary study indicate that pressure shock rather than cold shock is more beneficial for the commercial production of triploid turbot under farming conditions.